1. Technical Field
Exemplary aspects of the present invention generally relate to a liquid ejection head and an image forming apparatus including the liquid ejection head.
2. Related Art
Like a printer, copier, plotter, facsimile machine, or multifunction device having two or more of these capabilities, an inkjet recording device employing a liquid ejection recording method is also a type of image forming apparatus.
Typically, the inkjet recording device includes a recording head constricted of a liquid ejection head that ejects droplets of a recording liquid such as ink onto a sheet of a recording medium to form art image on the sheet.
The liquid ejection head has a nozzle face in which multiple nozzles, from which droplets are ejected, are formed. Ejection characteristics of the liquid ejection head, such as the volume and speed with which droplets are ejected from the nozzles, vary considerably depending on the shape and quality of each nozzle. It is also known that surface characteristics of a nozzle substrate, in which nozzle holes each forming the nozzle are formed, also considerably affect the ejection characteristics of the liquid ejection head. For example, adhesion of ink or the like to the area around the nozzle on a surface of the nozzle substrate may distort the trajectory of the droplets ejected from the nozzle.
To solve these problems, a liquid-repellent film is often formed on the surface of the nozzle substrate on a side from which droplets are ejected (hereinafter referred to as a droplet ejection side). As a result, the droplet ejection side of the nozzle substrate has a uniform surface across the surface of the nozzle substrate, thereby stabilizing the ejection characteristics of the liquid ejection head.
There is known a liquid ejection head in which a liquid-repellent film is formed across a surface of a nozzle plate up to an inner wall of each nozzle.
However, provision of the liquid-repellent film to the inner wall of the nozzle drastically affects capillary action in the nozzle at the edge of the film. Consequently, pinning occurs, in which the meniscus of the liquid in the nozzle is trapped at the edge of the liquid-repellent film, thereby distorting the trajectory of the droplets ejected from the nozzle or even blocking ejection of the droplets from the nozzle completely.